Presentations on subrings #
In this file we establish the API for realising a presentation over a
subring of R. We define a property HasCoeffs R₀ for a presentation P to mean
the (sub)ring R₀ contains the coefficients of the relations of P.
subring R₀ of R that contains the coefficients of the relations
In this case there exists a model of S over R₀, i.e., there exists an R₀-algebra S₀
such that S is isomorphic to R ⊗[R₀] S₀.
If the presentation is finite, R₀ may be chosen as a Noetherian ring. In this case,
this API can be used to remove Noetherian hypothesis in certain cases.
The coefficients of a presentation are the coefficients of the relations.
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The core of a presentation is the subalgebra generated by the coefficients of the relations.
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The core coerced to a type for performance reasons.
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A ring R₀ has the coefficients of the presentation P if the coefficients of the relations of P
lie in the image of R₀ in R.
The smallest subring of R satisfying this is given by Algebra.Presentation.Core P.
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The r-th relation of P as a polynomial in R₀. This is the (arbitrary) choice of a
pre-image under the map R₀[X] → R[X].
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The model of S over a R₀ that contains the coefficients of P is R₀[X] quotiented by the
same relations.
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(Implementation detail): The underlying AlgHom of tensorModelOfHasCoeffsEquiv.
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(Implementation detail): The inverse of tensorModelOfHasCoeffsHom.
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The natural isomorphism R ⊗[R₀] S₀ ≃ₐ[R] S.
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The presubmersive presentation on P.ModelOfHasCoeffs R₀ provided P.HasCoeffs R₀.
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An arbitrarily chosen relation exhibiting the fact that P.jacobian is invertible.
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A type class witnessing the fact that R₀ contains enough coefficients to descend
P to a submersive presentation.
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The jacobian of a presentation in the smaller coefficient ring, provided P.HasCoeffs R₀.
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The inverse jacobian of a presentation in the smaller coefficient ring,
provided P.HasCoeffs R₀.
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An arbitrarily chosen relation exhibiting the fact that P.jacobian is invertible,
provided P.HasCoeffs R₀.
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The submersive presentation on P.ModelOfHasCoeffs R₀ provided P.HasCoeffs R₀.